Alaska Railroad 4-6-2 "Pacific" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class 901 (Locobase 5095)

Locobase doesn't have much information about this Pacific, other than what was supplied on the elevation drawing found on . Works numbers were 62515 in December 1940 and 70336 four years later in December 1944.

The Alaska Railroad site -- (visited 22 Dec 2004) gives data that suggests this is the 801-series 4-8-2 with one less driving axle and consequently fire tubes that are 18" shorter. Otherwise the two boilers are the same. The firebox heating surface is likely to be virtually identical, although Locobase cannot confirm.

901 & 902 pulled both passenger and freight trains; 902 came in 1945. (1 Feb 2004) tells us that even though 901 was one of two locomotives involved in the only head-on collision the road ever had (on 19 October 1943), it carried on until 1952, when it was sold to FC Langreo in Spain but apparently never entered service.

NB: The direct heating surface (including the firebox heating surface) is an estimate calculated by subtracting the calculated tube heating surface from the reported total evaporative heating surface.

Specifications by Steve Llanso of Sweat House Media
Locobase ID5095
RailroadAlaska Railroad
Number in Class2
Road Numbers901-902
Number Built2
Valve GearBaker
Locomotive Length and Weight
Driver Wheelbase12'
Engine Wheelbase34.50'
Ratio of driving wheelbase to overall engine wheebase 0.35
Overall Wheelbase (engine & tender)69.29'
Axle Loading (Maximum Weight per Axle)
Weight on Drivers156200 lbs
Engine Weight249000 lbs
Tender Light Weight200300 lbs
Total Engine and Tender Weight449300 lbs
Tender Water Capacity10000 gals
Tender Fuel Capacity (oil/coal)14 tons
Minimum weight of rail (calculated)87 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter69"
Boiler Pressure200 psi
Cylinders (dia x stroke)22" x 28"
Tractive Effort33389 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.68
Heating Ability
Firebox Area295 sq. ft
Grate Area63 sq. ft
Evaporative Heating Surface2660 sq. ft
Superheating Surface646 sq. ft
Combined Heating Surface3306 sq. ft
Evaporative Heating Surface/Cylinder Volume215.92
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation12600
Same as above plus superheater percentage15120
Same as above but substitute firebox area for grate area70800
Power L118575
Power MT786.51


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